Isolation and characterization of Fc-receptors shed from human peripheral mononuclear cells.

Supernatants of human peripheral mononuclear cells containing membrane components shed in consequence of 4--37 degrees temperature shift were used as source for isolation of Fc-receptors (FcR). Aggregated IgG1 myeloma protein and TMV-anti-TMV complexes proved suitable sorbents to adsorb quantitatively and specifically the FcR-s. The isolated FcR interacts only with IgG and not with IgM. No haemagglutination was observed when the isolated FcR was incubated with sensitized human Rh+ red blood cells. Complement dependent lysis of sheep red blood cells was not inhibited by the isolated FcR-s. The interaction between IgG and SpA from Staphylococcus aureus (Cowan I) bacteria was not inhibited when red blood cells sensitized with IgG were preincubated with the isolated FcR-s. The differences between the FcR-like material isolated from supernatants of peripheral human mononuclear cells and those secreted by stimulated T cells or produced by lymphoblastoid cell lines are discussed.